1. Technical Background
The present invention relates generally to medical devices, and more particularly to a stent delivery catheter system.
2. Discussion
Catheter systems are used in a variety of therapeutic applications, including many vascular treatments. Various types of catheters are available, such as balloon catheters for procedures such as angioplasty. Angioplasty can be used to treat vascular disease, in which blood vessels are partially or totally or partially blocked or narrowed by a lesion or stenosis. By way of example, the present invention will be described in relation to coronary and peripheral angioplasty and other vascular treatments. The coronary procedure is often referred to as PTCA, which stands for xe2x80x9cpercutaneous transluminal coronary angioplastyxe2x80x9d. However, it should be understood that the present invention relates to any stent delivery system having the features of the present invention, and is not limited to angioplasty.
The present invention relates to a balloon catheter for positioning a stent, having a tubular basic body with a proximal and a distal end. Close to the distal end a balloon has been affixed to the basic body which is connected with an inflation lumen extending through the basic body. A stent in a compressed shape has been arranged around the balloon member.
In operation, such a balloon catheter is generally loaded at the distal end with a stent crimped around the balloon member and introduced into a patient, and maneuvered to the site where the stent is to be positioned. By supplying via the inflation lumen a medium under pressure to the balloon, the balloon will expand and consequently the stent as well. After expanding the stent to the desired size, the pressure exerted by the medium is relieved, as a result of which the balloon will tend to shrink again and come loose of the expanded stent. Next, the catheter may be removed from the body, leaving the stent behind at the desired site.
When introducing the catheter it is obviously very important that the stent remains positioned on the balloon in a reliable manner, until the desired position has been reached. Accordingly, it is desirable to provide a balloon catheter that enhances position retention of a crimped stent, especially when the catheter is advanced or withdrawn in use.
A balloon catheter according to the invention is distinguished in that a filling body of elastic material is arranged inside the balloon. This elastic filling body has a size corresponding to at least the dimensions of the inner diameter of the stent in contracted state, where the filling body is compressed by the stent in its crimped state. As the crimped stent has been more or less clamped on the elastic filling body, a resistance is provided against movement by the stent in relation to the balloon. When crimping the stent around the balloon and the filling body, the filling body will be compressed to some extent. Because of its elasticity, a radial force is exerted continuously on the inside of the stent, causing constant friction and enhancing the position retention of the stent.
The elastic filling body may be tubular in shape, or may have a spiral shape and be made of a pliable material, such that the flexibility of the catheter may be enhanced.
In addition, the elastic filling body may be radiopaque, and thus visible on an imaging screen during fluoroscopy. The radiopaque filling body would thus render separate marker bands unnecessary.
Visibility of the stent on the imaging equipment in the catheterization laboratory may be enhanced by providing two filling bodies that are positioned at a distance from one another. The stent would be directly visible in the space between the two filling bodies.
The balloon catheter may have a basic body arranged with an outer tube and an inner tube. The inner tube is received inside the lumen of the outer tube, and the elastic filling body may be mounted on the inner tube. The filling body may be affixed to the inner tube in any suitable manner, including an adhesive, or by selecting the internal diameter of the filling body to be smaller than the outer diameter of the inner tube. The filling body is thereby clamped onto the inner tube. According to another suitable embodiment, the filling body and the inner tube are formed at the same time by coextrusion.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.